1. Field of the Invention
The present invention is generally related to semiconductor wafer processing equipment and, more particularly, to an improved apparatus and method for controlling by-product formation and particle formation in a semiconductor wafer processing system.
2. Description of the Background Art
During semiconductor wafer processing, such as etching or deposition, unwanted particle formation may occur. For example, during a deposition process, undesirable by-products have been observed to result from the plasma itself. Alternatively, during an etching process, unmasked portions of a semiconductor wafer are etched by physical bombardment of ions from a plasma gas. Etching may occur through chemical reactions, illustratively occurring from concentrations of chlorine, fluorine, or a combination of both, reacting with the semiconductor wafer material. In either deposition or etching semiconductor wafer process, by-products from the plasma or substrate have been observed to condense and subsequently form a film on the surface areas of the various components in the processing chamber area.
One such component is a process kit that circumscribes a chuck assembly, which retains the wafer. The process kit includes one or more generally ring-shaped apparatus, commonly known as shadow rings, waste rings, or collars. Although an exhaust path in the chamber exists to eliminate by-products and exhaust gases, contaminating by-products have still been observed to form upon the process kit.
It has been observed that temperature control of the process kit is useful in managing film formation on the process kit. Utilizing, RF losses in the process kit may occur from the materials that the process kit is fabricated, therefore increasing the temperature of the process kit. In many instances, there are essentially no RF loses in the process kit. As such, the temperature of the process kit does not rise to a level that prevents condensation thereon. Furthermore, applying RF biasing to the process kit to generate plasma over the process kit does not allow direct control of the temperature of the process kit. In addition, ion bombardment may cause unwanted wear on the process kit, which also leads to undesired particle formation.
These unwanted by-products accumulate and cause numerous problems. One problem is that the deposits form a thick, highly stressed film that eventually flakes off the process kit surface into particles. The loose particles then become contaminants in the etching chamber, which may cause degrading characteristics to a wafer. For example, during an etching process, the unwanted particles act as a mask, which prevent the etch process from occurring beneath the particles. Furthermore, such contaminants may cause shorts between the etched traces of a wafer. In addition, such by-products and subsequent particle formation deteriorates the surface area of the process kit. Consequently, the life expectancy of the process kit is diminished, which increases the replacement costs.
Another problem is that deposition on the process kit surfaces adjacent to the wafer edge, as well as diffusion of etch products, are responsible for non-uniformity and drift of etch parameters across the wafer. The effect of deposition is a loss of a passivant at the wafer edge. A passivant is a material that deposits on the wafer during an etching process in order to protect the vertical profiles of the area of the wafer being etched. Therefore, a need exists in the art for an apparatus that actively and controllably prevents by-product formation on the process kit.
The disadvantages associated with the prior art are overcome by the present invention of an apparatus for controlling film formation about a periphery of a substrate. In particular, the apparatus is temperature regulated and reduces film formation about a periphery of a substrate during semiconductor wafer processing. In a first embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange. A collar is disposed over the peripheral flange defining a first gap therebetween, and circumscribes the chuck. Moreover, a heater element is embedded within the collar and adapted for connection to a power source.
In a second embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange, and a collar having a heating and chucking element embedded therein. The collar is disposed over the peripheral flange to define a gap therebetween, and circumscribes the chuck. Moreover, a pedestal having a gas delivery system therein is disposed below the chuck and collar.
In a third embodiment, the apparatus comprises a chuck having a chucking electrode and a radially extending peripheral flange, a collar, a pedestal, and a waste ring having a heating/chucking element embedded therein. The collar circumscribes the chuck, and is disposed over the peripheral flange and the waste ring. The waste ring is seated on the pedestal and comprises an electrode for chucking the collar to the waste ring, and chucking the waste ring to the pedestal. The waste ring and pedestal each have a gas delivery system for transferring heat from the bottom surface of the collar to the waste ring, as well as from the bottom surface of the waste ring to the pedestal.
Thus, the apparatus inventively provides the ability to controllably establish a surface temperature of the collar to prevent condensation and subsequently film formation thereon.